ZURICH, Sept 14 (Reuters) - Swiss packaging maker SIG Combibloc on Friday set the price range for its initial public offering at 10.50 to 13.50 Swiss francs per share, targeting proceeds of 1.05 billion euros ($1.22 billion) which will be used to trim debt.

As well as new shares being issued, Canadian private equity firm Onex, majority owner of the maker of the drinks packaging company since 2015, and SIG management will also sell some of their existing holdings. The float will be worth up to 1.78 billion Swiss francs ($1.84 billion).

Still, the existing shareholders will hold up to 56.4 percent in the company after the listing is completed and if an overallotment of shares is exercised.

The float would give SIG Combibloc a market capitalisation of 3.4 billion francs to 4.1 billion francs, with the company launching the bookbuilding process on Monday, Sept. 17.

It aims to begin trading on the SIX Swiss Exchange on or around Sept. 28 with a a free float of around 42.7 percent, or up to 49.1 percent if the greenshoe is used.

The packaging company, based near Schaffhausen on the Swiss-German border, has said it plans to use proceeds to cut debt to about 1.5 billion euros, or 3-3.25 times adjusted earnings before interest, taxes and depreciation (EBITDA) of 480 million euros, from about 2.5 billion now.

The float would be the tenth listing on the Swiss stock exchange this year and would mark a return of SIG to the bourse.

SIG Combibloc had been listed until 2007 as part of the Schweizerische Industrie Gesellschaft (SIG) conglomerate that once made everything from passenger trains to weaponry but over the years trimmed its focus to drink cartons.

BofA Merrill Lynch, Credit Suisse and Goldman Sachs International are acting as Joint Global Coordinators and Joint Bookrunners for the IPO.